#include<iostream>
#include<cstdio>
using namespace std;
long long a[9999999],b[9999999],c[9899999], n;
long double ans1=0,ans2=0,ans3=0,ans=0;
int main()
{
	cin>>n;
   for(int i=1;i<=n;i++)
   {
   	cin>>a[i];
   	ans1+=a[i];
   }
   for(int i=1;i<=n;i++)
   {
   	cin>>b[i];
   	ans2+=b[i];
   }
   for(int i=1;i<=n;i++)
   {
   	c[i]=a[i]-b[i];
   	ans3+=c[i];
   }
   ans=(ans1*3-ans2*2)/ans3;
	printf("%.6lf",ans);
	return 0;//谢谢~~
    
}  ```